Mammoth Cave National Park By: Mike Wallin
While cruising on Interstate 65 near west central Kentucky geologists start to see some interesting things with the road cuts. These road cuts along the highway show exposures of layered grayish rocks. These Layers of grayish rock the person sees shows openings in the stone. This is strong beginning evidence of one of the best examples of karst topography in the world. Karst topography is an erosion process that uses rain water and carbon dioxide gas form carbonic acid. The carbonic acid breaks down to make a hydrogen ion solution. Then the hydrogen solution and calcium carbonate (limestone) forms a calcium ion and a bicarbonate ion. Basically this breaks down the limestone and turns it into a solution causing Karst features called a cave. In Kentucky, on Interstate 65, is where the biggest cave system in the world is located(Harris,145). This cave system is called the Mammoth Cave National Park. This report will go over a brief history, the amazing features found in the park, and the stratigraphy of this area. Mammoth cave has been through many changes over the time it has been in existence. About 3000-4000 years ago Indians used the cave for shelter and minerals used in their medicines. Also in Mammoth Cave two Indian mummies were found in the cave. Later in Mammoth Cave history during the War of 1812 some of its passages were mined for saltpeter a main ingredient in gunpowder. Mammoth Cave was authorized as a natural park in the year of 1926. Lastly a cave research foundation was founded in 1957(Harris148). Many interesting karst features can be seen in Mammoth Cave. Click here to see an illustration shows karst topography features of Mammoth Cave, this illstration is from the National Park service. These cave features are called speleothems. In Mammoth Cave, many speleothems are seen such as flowstone, stalactites, stalagmites, and columns. Flowstone is made when cave water runs on a wall of the cave and forms a blanket looking thing. Another feature is stalactites these are icicle-shaped rock formation on top of the roof of the cave. Next are stalagmites these are poles of rock formed on the ground. Also columns are formed this is when stalagmites and stalactites converge into one single formation resembling a column. Other speleothems that are in Mammoth Cave include helictites, gypsum flowers, marbilite, and epsomite. In the time of 350 million years ago the continent of North America was farther south than it is today. Kentucky was about 10 degrees south of the equator. A shallow sea covered this entire area. Many organisms lived in this warm shallow continental sea. These organisms lived and died in this area. The dead bodies of the organisms accumulated and it started to form the huge layers of limestone. Mammoth Cave is placed within three limestone layersof the stratigraphy column: St. Louis, Ste. Genevieve, and the Girkin Formation.
The oldest limestone layer Mammoth Cave occupies is the St. Louis limestone. The limestone layer is about 200 feet thick and Mammoth Cave is located only in the upper part of the layer. Next is the Ste. Genevieve limestone layer. Mammoth Cave occupies the entire thickness of this 110 feet thick layer. The last and youngest limestone layer is the Girkin Formation. Mammoth Cave also occupies this formation in the 135 feet thick layer. Above these thick limestone layers lie the younger rock units of the Chester Series. The Chester series is a thick cap layer. This layer is mostly composed of sandstone. This sandstone is covered by a disconformity. Next a layer of Pennsylvanian conglomerates is found. This layer is only found on the northern part of the park. Over all the rock layers has about less than a degree dip. The cave system started to form in the late Paleozoic. At this time small cracks and fractures started to widen and become very small caves. Next the caves started to become wider and longer. The upper most levels formed 30 to 5 million years ago. The development of the lower levels of Mammoth Cave started during the Pleistocene and is still continuing today. Mammoth Cave National Park is one of the best examples of karst topography in the world. This national park is very useful to the geologists because it is a real working laboratory. Mammoth Cave has a rich history, many fine examples of karst features, and great stratigraphy of the area. Refrences Harris G.A. and Tuttle E,Geology of National Parks, Kendall/Hunt Puplishing Company, 1990, P.145- 158